Battery burn out / short circut

JonnyTwoCombs

Why would batteries short out in a gun

clubberlang12

The external resistance of the circuit is lower than the internal resistance of the battery. Wires from the positive terminals are touching the wires from the negative terminals of the battery before the have had a chance to pass through and area of resistance ie, fuse or motor. See if the wires coming from your battery are nicked near the battery itself and are touching each other forming a closed circuit.

JonnyTwoCombs

Thanks,

But I have checked the wiring, which is all new. This gun has now burned out 3 batteries.

clubberlang12

I'm conflustered then mate........hope you get it sorted soon.

JonnyTwoCombs

Me 2

Private Snafu

Did you check your connector? If you're using a Tamiya make sure the plastic divider is intact. Also did you buy a new wiring loom or make it up yourself?

se conman

I had a problem with damp hinge contacts on a scar (found by telebasher)

JonnyTwoCombs

lperrozzi wrote: »

Did you check your connector? If you're using a Tamiya make sure the plastic divider is intact. Also did you buy a new wiring loom or make it up yourself?

Its a M249 so I had to go all DIY on the wiring. The gun did work a few times after the re-wire as well.

I've checked the divided on the connectors on the gun and all the batteries and they all look fine.

Still confused......

Private Snafu

Take the electrics out of the gearbox (motor, wiring and microswitch) connect it up and see if it starts shorting outside the gearbox. If you're sure the wiring is 100% I'd take a good look at the microswitch itself. Did you solder the connections on the motor? If so make sure your solder isn't touching the gearbox shell:)

JonnyTwoCombs

lperrozzi wrote: »

Take the electrics out of the gearbox (motor, wiring and microswitch) connect it up and see if it starts shorting outside the gearbox. If you're sure the wiring is 100% I'd take a good look at the microswitch itself. Did you solder the connections on the motor? If so make sure your solder isn't touching the gearbox shell:)

Yeah they're all work outside the gearbox. The gearbox will turn fine (shoot)when outside the gun. Didn't solder the connections onto the motor, I used female spade connectors with heatsrink over them

I did replace the orginal microswitch with a 20A m/swtich I got in Maplins. But the gun worked fine after I did.

Sure is a puzzlier, isn't it

Private Snafu

Just reread my last post.... Meant to ask if you soldered the connections onto the microswitch

Weird alright.... You haven't installed a mosfet in it have you? I can't think of anything else without looking at it sorry

Firekitten

clubberlang12 wrote: »

The external resistance of the circuit is lower than the internal resistance of the battery. Wires from the positive terminals are touching the wires from the negative terminals of the battery before the have had a chance to pass through and area of resistance ie, fuse or motor. See if the wires coming from your battery are nicked near the battery itself and are touching each other forming a closed circuit.

To cut the story short. A short Circuit.

JonnyTwoCombs wrote: »

Thanks,

But I have checked the wiring, which is all new. This gun has now burned out 3 batteries.

Clearly, you havent checked it well enough, because its shorting somewhere.

JonnyTwoCombs

Firekitten wrote: »

Clearly, you havent checked it well enough, because its shorting somewhere.

It sure seems to be. But I have checked it a number of times. All the wiring is sealed, the connectings are insulated by heatsrink and the wiring to the battery connector is sound.

When out of the gun, the gearbox will fire. It's only when everything is fitted will the problem raise its head.

JonnyTwoCombs

Would it be the microswitch for any reason?

It's not an airsoft one, and the male connectors had to be filed down a bit so the female connector could slide on.

Firekitten

chances are, something, somewhere in the shell, or attached to it, touches gun when its in the reciver, causing a short. SOldering on the microswitch for example... *thinks where that is on the 249... its possible, and possible yoru gb is shimmed to tight, in the body it squeezes it shut and just refuses to turn.... so potentially stop pulling the trigger when it doesnt work!

sounds like theres no fuse in this gun (to flog a dead horse again) is there?

JonnyTwoCombs

Firekitten wrote: »

chances are, something, somewhere in the shell, or attached to it, touches gun when its in the reciver, causing a short.

How am I ever going to find that.

Firekitten wrote: »

SOldering on the microswitch for example... *thinks where that is on the 249

Contacts are push on, similar to the spade type used on AEG motors

Firekitten'70530486 wrote:

... its possible, and possible yoru gb is shimmed to tight, in the body it squeezes it shut and just refuses to turn.... so potentially stop pulling the trigger when it doesnt work!

Mmmmmmmm interesting. The gears spin quite free, but never the less I shall check again.

Firekitten wrote: »

sounds like theres no fuse in this gun (to flog a dead horse again) is there?

Aha! there is a fuse. I was using a 20A glass type. Not the overheat kind, but the kind that is supposed to breck and stop my expensive battery cooking :mad:

Firekitten

JonnyTwoCombs wrote: »

How am I ever going to find that.



Contacts are push on, similar to the spade type used on AEG motors



Mmmmmmmm interesting. The gears spin quite free, but never the less I shall check again.



Aha! there is a fuse. I was using a 20A glass type. Not the overheat kind, but the kind that is supposed to breck and stop my expensive battery cooking :mad:

Check if its the right amp rating for your gun... if its not, it just wont work. Gearboxes can get shim issues a lot... out of body... grand, in, just a tiny squeeze in the wrong spot, and it wont turn, but then again, it should blow when the motor cant turn.... fuse rating i suspect, is hinky.

clubberlang12

its possible, and possible yoru gb is shimmed to tight, in the body it squeezes it shut and just refuses to turn.... so potentially stop pulling the trigger when it doesnt work!

Aha! there is a fuse. I was using a 20A glass type. Not the overheat kind, but the kind that is supposed to breck and stop my expensive battery cooking

Since there is a fuse present, and presumably functioning properly, the problem lies along the wiring between the battery and the fuse. Resistance against the motor turning would cause over current blowing your fuse. If your fuse is working the short is happening before the fuse. It's creating a closed circuit before the fuse if you get what i mean. First get a meter and check your fuse is functioning.

Firekitten

As I said... check it works :P its a good start. Swap it to be safe, some can be too thick by accident. Or the gun needs a lower one.

A short before the fuse, would suggest the battery connectors... the tamiyas.... check both of those out, especially the gun side, as its 3 different batteries, we can presume, safely, its not a fault on them. Unless, you ripped the connectors off them all :P

clubberlang12

As Firekitten said, check your connecter that the battery connecter connects to. If it was one you make yourself the positive and negative heads may be touching which could cause a short there.

JonnyTwoCombs

Firekitten wrote: »

Check if its the right amp rating for your gun....

Its a 20A

Firekitten

but does the gun NEED 20, or lower?

NakedDex

20A is a bit high for most guns. Something a bit lower in a time delay is more preferable.

Anywho, when you say the gun has "burned out" three batteries, can you explain what you mean? What condition are the cells in? I'm going out on a limb here and saying it's actually your charging method.

JonnyTwoCombs

I've only got a 20A in because that was the rating of the original fuse in the gun, and it happily brapped away for over a year.

Thanks for all the ideas / suggestions folks, but I think I'm going to have to take it to my local shop.

No doubt the problem is something simple, so I'm a bit peeved I couldn't sort it out myself. :mad:

NakedDex

As I've mentioned elsewhere, it'll work no problem when the fuse is too big. You could put a nail in there and never worry about it again. The idea of the fuse is to be the weakest point of the circuit, and a fuse that's two big runs the risk of being stronger than the wiring it protects, making it redundant. If your wire can only take 15A, for example, but your fuse can take 20A, your wiring insulation (and maybe even the copper itself, if it's very fine/damaged) will melt long before your fuse blows.

JonnyTwoCombs

So, how did it work with the usual high standard :rolleyes: A&K are well known for, for so long with a 20A fuse fitted.

NakedDex

What I'm saying is that it can work fine with a 20A fuse, but if a fault develops in your system at 15A, your wiring/battery/switch/motor is going to be the one that gets destroyed, not the fuse. If you had no fuse in there it'd work too (hence the nail analogy).
It's nothing to do with being "high standard" or not. It's simply down to whether a fault occurs.


Here's a prime example: I have a G&G SR25. One of my outright favourite rifles for a number of reasons. Due to the type of gearbox, it needs 9.6V packs just to operate it's semi-only firing. Rapidly firing it in semi, however, blows the fuse.
If there was no fuse, it'd continue to operate, but continuing to rapidly fire would melt the insulation, destroying the wiring loom, causing a short circuit and destroying the battery and/or motor. It wouldn't happen straight away, but it'd happen inevitably.

Anyway, we're straying off point here. If your wiring loom is ok, and your connector shows no sign of damage, then your problem is - from my estimation of the symptomns you describe - in your charging method.
What type of battery packs were "burned out". Voltage, current and chemistry?

JonnyTwoCombs

Yeah, I'm with you now Dex (or rather catching up).

The batteries are run of mill ASG 9.6 2000mah types. I'm unsure of the chemistry as I don't have them in front of me.

I might try a lower rated fuse before heading to the techie.

One other (possibly stupid) question. When a battery shorts, is it a total goner or can some of the cells be rescued?

NakedDex

I'm unfamiliar with ASG packs so I'd need to know the chemistry before making any further hypothesis on whether this is related directly.
What charging method/settings do you use, and how often were these packs charged before they "burned out"?


Packs can, sometimes, be rebuilt, but it's often more expensive than getting a new pack. Individual tagged cells are available from the likes of Radionics, but you'd have to first check each cell in turn to see how many have failed.
I've rebuilt plenty of packs before, but for power tools like cordless angle grinders and drills where the new battery pack was twice the cost (or more, in many cases) of the cells I'd need to rebuild the pack from scratch.
In airsoft, however, you're almost always better off just getting a new pack, simply because the end cost is far cheaper. You could, of course, scavenge the good cells from your failed battery and keep them as spares for the future if you wished.